Risk assignment in pediatric soft-tissue sarcomas: an evolving molecular classification.

Pediatric soft-tissue sarcomas are increasingly being defined by both histologic appearance and underlying chromosomal abnormalities to determine their biologic behavior. Most sarcomas of this type have specific chromosomal translocations that create unique fusion genes. Expression of such fusion genes may have diagnostic, prognostic, and surveillance implications for the patient. This review analyzes the fusion gene expressions seen with seven of the major types of pediatric soft-tissue tumors and their impact on biologic behavior. In nearly 50% of the malignancies discussed, the diagnostic, prognostic, and surveillance implications of their specific fusion gene expressions are already defined or becoming established (alveolar rhabdomyosarcoma, Ewing sarcoma/primitive neuroectodermal tumor, and synovial sarcoma). In the remainder of the tumors, these questions are rapidly being addressed. To facilitate future fusion gene studies, pediatric surgeons, pathologists, and oncologists need to work as a coordinated team to ensure proper tumor procurement. Large clinical cooperative trials involving biologic studies of pediatric soft-tissue sarcomas could facilitate advancement of knowledge in this area of pediatric oncology.